A Positive Airway Pressure (PAP) device is used in the treatment of sleep related breathing disorders such as Obstructive Sleep Apnea (OSA). Colin Sullivan was the first to invent the use of nasal Continuous Positive Airway Pressure (CPAP) to treat Obstructive Sleep Apnea (OSA), e.g., see U.S. Pat. No. 4,944,310. OSA is characterized by partial or complete occlusion (i.e., apnea) of the upper airway passage during sleep. OSA sufferers repeatedly choke on their tongue and soft palate throughout the entire sleep period resulting in lowered arterial blood oxygen levels and poor quality of sleep.
CPAP treatment generally provides a supply of air or breathable gas from a blower to a patient via an air delivery conduit and a patient interface, such as a full-face or nasal mask or nasal prongs. The air or breathable gas is commonly delivered at a pressure of 4 cm H2O to 28 cm H2O and acts as a splint to hold the airway open during sleep. CPAP therapy has been shown to effectively eliminate both snoring and obstructive sleep apneas. However, some patients complain of discomfort with CPAP therapy.
The pressure required for effective CPAP therapy differs between patients. In order to determine an individual's effective CPAP therapy pressure, the individual generally undergoes a sleep study in a hospital, clinic or sleep laboratory. A complete sleep study commonly occurs over two nights, with diagnosis of OSA occurring the first night and pressure titration occurring the second night. On the first night, the individual is observed while asleep and parameters such as oxygen saturation, chest wall and abdominal movement, air flow, expired CO2, ECG, EEG, EMG and eye movement are recorded. On the second night, the individual is provided with nasal PAP therapy and the delivered treatment pressure is altered in response to the presence of snoring or apneas. The minimum pressure required during the night to eliminate the snoring and apneas is determined to be the effective PAP therapy pressure.
Because breathing against a pressure elevated above ambient pressure can be uncomfortable, especially when trying to sleep, it is desirable to keep the PAP pressure as low as practicable, particularly if the individual requires long term treatment. Lower PAP pressures also result in a lower mask contact pressure which is generally more comfortable for the user. Thus, during PAP therapy it is desirable to use the lowest practicable treatment pressure that is effective in preventing occlusion in order to provide the higher levels of comfort and thereby promote compliance with treatment.
Another type of CPAP device known as a Bilevel CPAP device provides a first pressure during inhalation (commonly termed an IPAP) and a second, lower pressure during exhalation (commonly termed an EPAP). Some patients perceive that the lower pressure during exhalation is more comfortable, at least while they are awake. Examples of these devices include the ResMed VPAP® series, and the Respironics BiPAP® series. Bilevel CPAP devices may be prescribed for patients who are not compliant with single pressure CPAP devices.
A further type of CPAP mode designed to enhance patient comfort and compliance provides a rapid decrease in pressure at the beginning of expiration and then quickly returns to therapeutic pressure at or near the end of expiration. These algorithms are designed to overcome the perceived problem of exhaling against a high pressure and are termed Expiratory Pressure Relief (EPR) modes. This mode forms the basis of Respironics C-Flex mode. See published applications WO 2005/065757 and WO 2004/112680 and U.S. Pat. Nos. 5,535,738; 5,794,625; 6,105,575; 6,609,517; and 7,128,069.
Another way of improving patient comfort and compliance is to start each therapy session at a low therapeutic pressure (e.g., 4 cm H2O), and then ramp up to full therapeutic pressure over a period of time such as the first hour. This allows the patient to adjust to the sensation while falling asleep. Alternatively, the device may be set to implement a time delay before full therapeutic pressure is applied, which allows the patient time to fall asleep before full therapeutic pressure is applied. See U.S. Pat. Nos. 5,199,424 and 5,522,382.
Another form of CPAP therapy can be provided by an automatically adjusting CPAP device such as the ResMed AUTOSET™ SPIRIT™ device. In this device, the CPAP pressure is automatically increased or decreased in accordance with indications of flow limitation, such as flow flattening, snore, apnea and hypopnea. See U.S. Pat. Nos. 5,704,345; 6,029,665; 6,138,675; and 6,363,933. These patents also describe a method and apparatus for distinguishing between so-called “central” and obstructive apneas. More recently, automatically adjusting Bilevel devices have been described where both the IPAP and the EPAP pressures are capable of being automatically increased or decreased in accordance with indications of flow limitation as described above. See pending patent application WO 2005/063323.
An advantage of an automatically adjusting system is that it provides the patient with an elevated PAP only when required. This means that the patient is spared the discomfort of receiving the highest treatment pressure during the whole treatment session. Furthermore, while the treatment pressure required for a particular patient may vary over time, a correctly functioning automatic system can obviate the need for the patient to return for a subsequent sleep study to reset the treatment pressure delivered by the PAP device.
Generally, PAP devices are made and tested to work most efficiently with particular patient interface systems. However, the PAP devices and patient interface systems are sold as separate components of the therapy equipment. Thus, patients may decide to use a particular PAP device together with a patient interface system that was not specifically tested for that PAP device. This may result in a less than efficient therapy system. Therefore, a system that encourages consumers to buy compatible products may provide more efficient and/or comfortable therapy. Once compatible products are combined, they may deliver enhanced therapy benefits compared to the separate products alone.
The contents of all of the aforesaid patents are incorporated herein by cross-reference.
The present invention provides improvements to known PAP devices to enhance and/or facilitate the treatment session.